Offshore platforms may need to be dismantled either for decommissioning after their useful lives or for installing new platforms at the same locations to accommodate more equipment or wells (both). Installing and commissioning an offshore platform can involve placing a large structure on a mudline, or seabed, within a body of water. In the case of a jacketed platform, a steel frame structure is secured to the mudline with piles. A portion of the structure surrounds, or “jackets” the piles. Dismantling involves removing the platform sufficiently so that it does not create a navigation hazard, cause any harm to the environment or facilitate installation of a slip-over platform. In the case of fixed offshore platforms, such removal often involves a near complete removal of the fixed platform since fixed platforms are often installed in shallow bodies of water. Removal of fixed platforms down to a mudline of a body of water is common.
In the case of a jacketed platform, removal often involves cutting a structural pile from within the pile a few feet below the mudline. This operation can involve cutting the pile from the pile's interior, lowering explosive charges into the piles, or other methods of cutting from the interior of the pile such as water jetting. The latter can disturb the seabed or degrade the seabed soil (or both).